There are three likely places water will flow into the outboard transmission, the shift rod seal, the input shaft seal and the output shaft seal or a combination of two of them.

Whatever you do you will have messy oil and the need to clean and degrease stuff properly.

its time to clear and clean the workbench, remove the lower leg and rebuild the transmission. Look carefully at the shift dogs for wear on the corners, any damage on the dogs and its time to replace at least the shift dog to get the most out of your rebuilt gearbox. Obviously new seals and gaskets plus a good look at the water pump are easy checks while its all on the bench.

Most times changing just one seal does not find all the issues, its probably just as fast to do the lot and be sure of what you've got.

_________________RL24 Mk4 cruiser Mariner 5 2 stroke

A bad day in the Whitsundays is better than a good day at work. Unless you work in the Whitsundays.

For this message the author INMA has received thanks: bunyip (Mar 12th, '17, 08:23)

Thanks INMA - all you have said here is spot on.However here's what i have learnt after a little research:

You can prove which of the 3 locations is causing the problem by removing the gear oil, and pressurising the gear box with some compressed air (probably best by hand), then spraying some soapy water around the 3 seals observing for bubbles.

The prop shaft seal can be inspected in situ however the top seals require the lower unit to be removed to get access to the top of the water pump assembly.

Sooooo, since i replaced the water pump impeller last year which involved lower unit and water pump removal and reassembly, i am hoping the top seals are still ok and will concentrate on the prop shaft.

The pneumatic test shown proves nothing. Air is a small molecule so it will pass where oil won't pass. Water being the problem, it capillaries past the seal emulsifies with the oil and may onlybe doing it as the shafts move.

And the leak could be something that only occurs when the shaft turns or moves axially under load.

Back to my original advice, rebuild it properly, do it once and avoid future problems.

_________________RL24 Mk4 cruiser Mariner 5 2 stroke

A bad day in the Whitsundays is better than a good day at work. Unless you work in the Whitsundays.

Without making your problem too technical, in most cases water gets in the leg through output shaft seal and in my case, through corrosion on the casting body, where O ring seal the joint. From the top it can too, but not likely. To get the aluminum bearing body and shaft out, you have to have puller, I did make one, but don’t know where it is and it was a few years back. I grinder off the corrosion and use Davko putty to fill the surface, and then sand it to right shape. After ensemble, I did not have problem since.

And also I painted the repair surface by etching primer and top it up with marine top coat.

Good luck, regards Frank

For this message the author Frank Peters has received thanks: bunyip (Mar 12th, '17, 08:24)

Without making your problem too technical, in most cases water gets in the leg through output shaft seal and in my case, through corrosion on the casting body, where O ring seal the joint. From the top it can too, but not likely. To get the aluminum bearing body and shaft out, you have to have puller, I did make one, but don’t know where it is and it was a few years back. I grinder off the corrosion and use Davko putty to fill the surface, and then sand it to right shape. After ensemble, I did not have problem since.

And also I painted the repair surface by etching primer and top it up with marine top coat.

Good luck, regards Frank

Thanks for the response Frank. Was yours the same model OB?I drained the box then began to undo the bolts shown in my first pic, and the shaft bearing bracket started to move rearward by itself...magic. That's when i got a little nervous that part of the shaft assembley was perhaps spring loaded or something.

So i put it all back together to do some research.Here's what i found online:

Attachment:

bf8a.jpg [ 89.12 KiB | Viewed 1812 times ]

Can anyone point out to me exactly on this diagram where the "water seal" actually resides?Its listed as a component but no arrow to the diagram.

Bunyip, It will be inside the Shaft Holder. Instructions say remove the bearing to gain access to the seal.

You may get lucky in removing the bearing by using a thick pin punch from the propellor side. This is not ideal if you are planning on reusing the bearing, but since you are doing the seal then a new bearing is good insurance.

Be very glad the Honda shaft holder slides out because the Yamaha version is a nightmare.

Cheers

jeff

_________________"There is no perfect boat. There are only those shaded to your preferences.":-)

There is also an "O" ring in a groove on the outside of the Shaft Holder. Check it to see if it is still circular in cross section and hasn't been flattened a bit.The pressure of the Shift Spring is what caused the Shaft Holder to come off by itself. My guess would be the "O" is probably the source of your leak. Fit a new "O" ring before you remove the seal and bearing and try it under load. Gently and thoroughly clean the "O" ring seat on the shaft holder and where the "O" ring mates in the leg casing using a BLUE scourer. Don't use the GREEN ones as they will scratch the Aluminium surface.Liberally lubricate both surfaces with PBR Rubber Grease (Available from Brake Repair places) before you reassemble and make sure you do each bolt up a little at a time to make sure the shaft holder sits square in the case. Good Luck, take and post lots of pics

For this message the author Ukuri has received thanks: bunyip (Mar 12th, '17, 08:25)

Ukuri - thanks for the post. Great suggestions there.Since there is only a very small amount of water in the box (after 2 years) i am pausing on this project having replaced the gear oil as i am working till my next trip and won't have time for a 'play' till i return return.

Do you have the same/similar model? Can you tell me if the dog gear on the output shaft will simply disengage on withdrawal then reengage during reassembly?

Jeff/Frank - i can't knock out the bearing as there is no exhaust outlet holes in the bearing bracket, so will need a puller...TBA.AZ - will order new fibre washers.

I have a BF5A which looks remarkably like the drawing you posted.I have a Honda EPC (Electronic PParts Catalogue) programme installed on my computer. I "acquired" it via a Torrent site some time ago but sadly I have lost the original "zip" file due to another hard drive failure. It has exploded parts lists, complete with part numbers and prices, for all Honda outboards up to about 2010.Take a high res pic of the Identification Plate and post it and I'll see if I can find some info for you.I lost one of the washers so I used the one for the flushing bolt on the Oil Drain Bolt and made one up for the Flushing Bolt out of "fibre" (the dark red stuff electrical fitters use. You can buy sheets in various thicknesses from a mob in Melbourne).

Can you tell me if the dog gear on the output shaft will simply disengage on withdrawal then reengage during reassembly?

A. Yes, readily. I think the manual recommends that you have it in forward (or was it reverse) to remove the shaft holder. This is so there is pressure rearwards (ie towards the prop) which is what caused the shaft holder to come out by itself. Memory is a little hazy now but it wasn't difficult at all to disassemble or reassemble.

Mine had water in it so I went to a combination of Marine Grease and Gear Oil. DONT DO THIS! WAS A MISTAKE. The water displaced the oil and the grease went hard and caused the rearmost bearing (reverse) to dry out and sieze somewhat. Probably because reverse is hardly ever used. It caused some slight wear on the reverse bevel gear boss that should be a tightish fit to the bearing. I caught it in time and once cleaned up the bearing and shaft are OK.Bloody HONDAS are bullet proof and mine keeps going using almost no fuel. I have never been very impressed with it as it is just not powerful enough to drive a Careel and you cannot fit an alternate prop to it. I'm hoping it will die so I can buy a Tohatsu but it just won't die so I am stuck with it.

The bigger challenge was in removing the water seal located underneath the bearing. This was removed the same way but was completely destroyed in the process. Care must be taken not to pit the seal seat with the punch.

When installing new seal, take care to insert the correct way round. That is with the seal's stainless spring facing into the gearbox (not facing the prop). It is hard to get in completely as its a tight fit and you need the exact right size socket to send it home with a hammer.

Make sure you set it deep enough so that the bearing is free to rotate without rubbing on the seal. I made this mistake first and the bearing would not rotate due to contact with the rubber seal, and had to remove the bearing and set the seal deeper.

Otherwise a fairly easy job overall.Thanks to all the topic responders for help and advice.

The location of the water seal is not clearly shown in the exploded diagram further back. The image below shows the seal still in place after the bearing has been removed from the bearing bracket. The orientation of the seal is also demonstrated with the spring facing into the inside of the gearbox.

Yes happy to get it done - happy to keep the wallet closed - and a boost to the confidence for tackling future projects.Good to take a look inside the gearbox too and see the state of the gears. All helps in the decision making process when it comes to deciding whether or not to spend time and money on maintaining a 20 y.o. outboard going forward.

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